High rate induction system

ABSTRACT

A sortation system and method of inducting product are useful with a sorter having a continuous member defining a plurality of transport positions of the continuous member and a plurality of sort destinations for receiving product discharged from the continuous member. At least one induction unit is provided including a plurality of tandem conveying units. Product is received with the at least one induction unit from a product source and discharged from the at least one induction unit to the continuous member. According to one aspect of the invention, the at least one induction unit follows the speed of the continuous member. This includes starting as soon as the continuous member is moving and decreasing in speed substantially only when the continuous member decreases in speed. The invention is useful with linear sorters, such as positive displacement sorters, and the like. The invention is also useful with carousel sorters, such as tilt-tray sorters and cross-belt sorters.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.09/669,170, filed on Sep. 25, 2000, now U.S. Pat. No. 6,513,641, whichclaims priority from U.S. provisional patent application Ser. No.60/158,679, filed on Oct. 12, 1999, the disclosures of which are herebyincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

This invention pertains to conveyor sortation systems and, inparticular, to a method and apparatus for inducting product to a sorter,wherein the sorter includes a continuous conveying member defining aplurality of transport positions and a plurality of sort destinationsfor receiving product discharged from the continuous member. Theinvention has application to both linear sorters, such as positivedisplacement sorters, and carousel sorters, such as tilt-tray andcross-belt sorters.

The quintessential goal for any material-handling system is to maximizethe throughput of product through the system. In the case of a sorter,it is known that the throughput of the sorter is limited by the abilityof the system to induct product to the sorter at a rate that matches thethroughput of the sorter, with adequate gaps between the product. If aninsufficient rate of product is supplied to the sorter, then the sorterbecomes starved and is incapable of meeting its rated throughput.

A common technique for keeping the sorter supplied with product is tobuild accumulation into the system upstream of the induct. With abacklog of product at the input to the induct, the function of theinduct becomes limited to ensuring that adequate product gaps aredeveloped and, in the case of multiple-line inducts, that the productsare merged together from the multiple lines. However, accumulation comesat a cost and is not always feasible. For example, some systems requirethat substantially all of the conveyors be of the belt variety. This isespecially common in the parcel-handling industry where packages may bepoorly packaged and may include protruding items from the packages. Theuse of live-roller conveyors, which are the common form of accumulation,is considered to be inappropriate for handling such parcels.Accordingly, the ability to induct product to the sorter at an adequaterate becomes difficult when accumulation upstream of the sorter is notpractical, such as where the conveyors are of the belt variety.

Carousel-type sorter systems are known to be able to handle product of awide range of characteristics and can be compact and configured in manydifferent ways. In particular, the induct systems and the destinationchutes, or conveyors, can be arranged at any place along the carouseland can be arranged on one or both sides of the carousel. In order toprovide maximum product throughput with a carousel sorter, empty unitsare booked, or reserved, for product positioned on the induct. However,a particular timing window must exist in order to accelerate the productto the speed of the carousel to meet the booking requirement for aparticular empty carrying unit. If this window cannot be met, it isnecessary for the carrier to pass by the induct without a product beingloaded on that unit. It should be apparent that the more carriers thatpass by the induct without receiving a product, the lower the throughputof the carousel-type sortation system. Conversely, the throughput of acarousel-type sorter can be increased by ensuring a maximum loading ofthe carriers passing by an induct.

SUMMARY OF THE INVENTION

The present invention provides a sortation system and a method ofinducting to a sortation system which increases the performance of thesorter by ensuring an improved supply of product to the sorter.

A sortation system and method of inducting product to a sorter,according to an aspect of the invention, is useful with a sorter havinga continuous member defining a plurality of transport positions of thecontinuous member and a plurality of sort destinations for receivingproduct discharged from the continuous member. An induction system isprovided that includes at least one induction unit having a receivingend for receiving product from a product source and a discharge end fordischarging product to the continuous member. The at least one inductionunit includes a plurality of tandem-conveying units between thereceiving end and the discharge end and a control controlling theconveying units. According to this aspect of the invention, the at leastone induction unit follows a speed of the continuous member. Thisincludes starting substantially as soon as the continuous member ismoving and decreasing in speed substantially only when the continuousmember decreases in speed.

This aspect of the invention allows an induction system which does notrequire accumulation upstream of the induction system. Furthermore,bookings of product on the induction unit can be maintained,notwithstanding variation in speed of the continuous member.

A sortation system and method of inducting product to a sorter,according to another aspect of the invention, is useful with a sorterhaving a continuous member defining a plurality of transport positionsof the continuous member and a plurality of sort destinations forreceiving product discharged from the continuous member. An inductionsystem is provided having at least two induction units. Each of theinduction units has a receiving end for receiving product from a productsource and a discharge end for discharging product to the continuousmember. The sorter further includes a control which determines gapbetween product that will be discharged to the continuous member. Theinduction unit is capable of discharging product to the continuousmember irrespective of the gap between product.

This aspect of the invention also facilitates the ability of theinduction unit to follow the speed of the continuous member because itis not necessary to shut down the induction unit when a product havingan improper gap is detected. Rather, the product with the improper gapmay be discharged to the continuous member and either sorted to aspecial lane or recirculated to the induction subsystem.

A sortation system and method of inducting product to a sorter,according to another aspect of the invention, is useful with a sorterincluding a continuous member defining, a plurality of transportpositions of the continuous member and a plurality of sort destinationsfor receiving product discharged from the continuous member. Aninduction system is provided having at least one induction unit with areceiving end for receiving product from a product source and adischarge end for discharging product to the continuous member. The atleast one induction unit includes a plurality of tandem conveying unitsbetween the receiving end and a discharge end and a control forcontrolling the conveying units. According to this aspect of theinvention, the control books at least one transport position for receiptof product from the at least one induction unit. The control books atransport unit for a product when that product is at a booking conveyingunit and adjusts relative spacing between a product and the respectivetransport position booked for that product on the conveying unitsdownstream of the booking conveying unit.

This aspect of the invention allows multiple product to be booked on theat least one induction unit and awaiting discharge to the continuousmember. Furthermore, by booking the transport position for a product atan upstream portion of the at least one induction unit enhances theability of the induction system to ensure an acceptable gap between theproducts discharged to the continuous member.

A sortation system and method of inducting product to a sorter,according to another aspect of the invention, is useful with a carouselsorter having a plurality of product carriers arranged in an endlessloop and a plurality of sort destinations for receiving productdischarged from the carriers. An induction system is provided having atleast one induction unit with a receiving end for receiving product froma product source and a discharge end for discharging product to thecarriers. The sortation system further includes a control for monitoringproduct on the carriers and booking carriers for product on theinduction system. The control is capable of booking carriersirrespective of whether the carriers are already carrying product.

This aspect of the invention facilitates the booking of carriers well inadvance of the induction system, thereby increasing the number ofcarriers that can be booked at the induction system. If a carrier thatis carrying a product is booked, but is unable to discharge its productprior to arriving at the induction system, the booking may be cancelled.

These and other objects, advantages and features of this invention willbecome apparent upon review of the following specification inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a sortation system, according to theinvention;

FIG. 2 is the same view as FIG. 1 of an alternative embodiment;

FIG. 3 is a top plan view of a single-line induction system, accordingto the invention;

FIG. 4 is a side elevation taken from the direction IV—IV in FIG. 3;

FIG. 5 is an end elevation taken from the direction V—V in FIG. 3;

FIG. 6 is a top plan view of a multiple-line induction system, accordingto the invention;

FIG. 7 is a side elevation taken from the direction VII—VII in FIG. 6;

FIG. 8 is a side elevation taken from the direction VIII—VIII in FIG. 6;

FIG. 9 is an end elevation taken from the direction IX—IX in FIG. 6;

FIG. 10 is a diagrammatical representation of the single-line inductionsystem in FIGS. 3-5;

FIG. 11 is a diagrammatical representation of the multiple-lineinduction system illustrated in FIGS. 6-9;

FIG. 12 is a diagrammatical representation of a conveying unit used inthe invention;

FIG. 13 is a diagrammatical representation of the upstream portion of aninduction unit;

FIG. 14 is a flowchart of a regulation phase of a belt-moving strategy;

FIG. 15 is a flowchart of a transition state for the upstream-mostconveying unit;

FIG. 16 is a flowchart of a transition state for the second conveyingunit from the product input;

FIG. 17 is a flowchart of a transition state diagram for the conveyingunits between the second from the product input and the second from theclosest to the product output;

FIG. 18 is a flowchart of a transition state diagram of the conveyingunit closest to product output;

FIG. 19 is a flowchart of an activation sequence function;

FIG. 20 is a flowchart of a line synchronization function for a primaryinduction line; and

FIG. 21 is a flowchart of a line synchronization function for asecondary induction line.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings, and the illustrativeembodiments depicted therein, a high rate induction system 30 is usedwith a sortation system 25 including a continuous member 26 and aplurality of sort destinations 28 for receiving products discharged fromthe continuous member (FIG. 1). In the illustrative embodiment,continuous member 26 is a sortation conveyor and, preferably, a positivedisplacement sortation conveyor utilizing pusher shoes which travel withthe conveying surface, as disclosed in commonly assigned U.S. Pat. No.5,127,510 entitled MODULAR DIVERTER SHOE AND SLAT CONSTRUCTION, thedisclosure of which is hereby incorporated herein by reference. However,the invention is useful with other types of sortation systems known inthe art such as tilt wheel sorters, transverse belt sorters, stationarypusher sorters, and the like. Sort destinations 28 may include takeawayconveyors, chutes, or the like, on one or both sides of continuousmember 26.

High rate induction system 30 includes at least one and, possibly, twoor more induction units 32, each having a receiving end 34 for receivingproduct from a product source 46 and a discharge end 36 for dischargingproduct to continuous member 26. Each induction unit 32 is made up of aplurality of conveying units 38 which are arranged in tandem betweenreceiving end 34 and discharge end 36. The sortation system furtherincludes a control 40 which controls induction system 30 in conjunctionwith the components of sortation system 25. Especially, when more thanone induction unit 32 is included, the induction units discharge theirproduct to continuous member 26 through a merge 42.

At least one induction unit 32, designated a primary unit, follows thespeed of continuous member 26. The primary induction unit 32 starts assoon as the continuous member is moving and decreases in speed only whenthe continuous member decreases in speed. This is particularlyadvantageous when the product source 46 does not provide accumulation,such as when the product source is made up of belt conveyors. Althoughcontrol 40 operates induction system 32 in order to create particulargaps between product discharged to continuous member 26, under certaincircumstances, it is not possible to create a sufficient gap to allowthe product to be sorted. In a particular mode of operation, primaryinduction unit 32 is allowed to discharge product, or packages, tocontinuous member 26, even if a proper gap will not exist between theproduct. Under such circumstances, product may be returned to theinduction system by a recirculation line 44, which itself may precludeaccumulation, such as by being made up of belt conveyors.Advantageously, this mode allows master induction units 32 to beoperated continuously without stopping. This provides a priority lanefor feeding product to the continuous member 26 without substantialinterruption.

Control 40 matches, or books, a particular location on continuous member26 for a product shortly after arriving at receiving end 34. Inparticular, the booking occurs, preferably, no later than the thirdconveying unit 38 from receiving end 34. The remaining of the conveyingunits between the booking conveying unit and the discharge end 36 adjustthe relative spacing between the product and the respective transportposition booked for that product on the continuous member. In thismanner, multiple product can be booked on the induction unit 32 awaitingdischarge to continuous member 26. Preferably, the leading edge of aparticular pusher shoe on continuous member 26 is used as the transportposition, or logical all, for booking a product.

Another embodiment of a high rate induction system according to oneaspect of the invention, is illustrated in a sortation system 25′including one or more induction systems 30 a, 30 b, a continuous member26′ and a plurality of sort destinations 28′ for receiving productdischarged from the continuous member (FIG. 2). The induction system ofsortation system 25′ may include a multiple-line induction system 30 a,made up of two or more induction units 32, or an induction system 30 b,including a single induction unit 32. Each induction unit 32 isidentical with that utilized with sortation system 25. However, ratherthan utilizing a merge 42 to transition product from the discharge end36 to continuous member 26, induction system 30 a, 30 b utilizes atransition 48 which is oriented at an acute angle, such as 45°, withcontinuous member 26′. Continuous member 26′ is a carousel-type sortermade up of a plurality of carriers 50 arranged in an endless loop,substantially horizontal, as disclosed in commonly assigned U.S. Pat.No. 5,588,520, entitled CROSS-BELT SORTATION SYSTEM, the disclosure ofwhich is hereby incorporated herein by reference. Two known types ofcarousel-type sorters are cross-belt sorters and tilt-tray sorters,although variations of these types of sorters are known in the art. Sortdestinations 28′ may be chutes, gravity conveyors, or the like, forreceiving product discharged from continuous member 26′. In theillustrative embodiment, sort destinations 28′ are arranged on oppositelateral sides of continuous member 26′, but may be positioned on onlyone side thereof. By its nature, product inducted by induction systems30 a, 30 b may be sorted to substantially any sort destination 28′ insortation system 25′. Therefore, it is common for a product carrier ofcontinuous member 26′, which collectively travels in an endless loop, topass an induction system with a product on that carrier. When a carrierpasses an induction system with a product on that carrier, it is notpossible for the induction system to place a product on that carrier.

Control 40′ books one of the carriers 50 for product received atreceiving end 34. Preferably, by the time the product reaches the thirdconveying unit 38 from receiving end 34, control 40′ can book thatproduct with a carrier 50. According to the invention, the control iscapable of booking carriers, even when a carrier is already carryingproduct. For example, in the illustrative embodiment, carrier 50 may becarrying a product for discharge at one of the sort destinations 28′ atthe top of FIG. 2. Control 40′ is aware of the destination of thepresent product on carrier 50 and thereby allows carrier 50 to bebooked. If carrier 50 is unable to discharge its product at the intendedsort destination prior to arriving at induction system 30 a, such asbecause the destination is full or jammed or the like, control 40′rescinds the booking of that carrier and another carrier is booked forthat product.

Each induction unit 32 includes a frame 52 which supports the conveyingunits 38. Frame 32 defines at least one horizontal surface 54 laterallyoffset from the conveying units (FIGS. 3-9). Horizontal surface 54supports a plurality of control input devices 56 and a status indicator58. The control input devices may include, by way of example, a “start”switch, a “stop” switch, and the like. Status indicator 58 may includemultiple color indicators, such as green, yellow, and red, in order toindicate the status of the induction unit 32. Frame 52 additionallyincludes support legs 60 which define therebetween a control receivingcompartment 62. Control receiving compartment 62 supports a controlassembly 64. By positioning control assembly 64 in control compartment62 between legs 60, a necessity for a standalone control cabinet knownin the art is preferably obviated. Furthermore, the incorporation ofcontrols 56 and status indicator 58 into frame 52 incorporates all ofthe control functions within the outline of induction unit 32. This notonly allows the induction unit to be more aesthetically pleasing, italso places the controls closer to items that are being controlledthereby.

Each conveying unit 38 includes a belt 66 which extends substantiallythe width of the conveying surface defined by the conveying units 38.Belt 66 is drivingly supported by a driving roller 68 and an idlerroller 70. Driving roller 68 is rotated by a servomotor 72, which drivesdrive roller 68 through a V belt, cog belt, chain, or the like.Servomotor 72 is either a DC-operated servomotor or a variable frequencyAC motor of the type well known in the art. A belt tensioner 74 providesadjustment to the tension of belt 66.

A photo-eye 76 directs a beam between the belts 66 for adjacentconveying units 38 in order to detect the passage of a product from onebelt 66 to the downstream tandem belt 66. One such photo-eye ispositioned upstream of each conveying unit 38. The construction of eachconveying unit 38 facilitates a rapid replacement of the associated belt66. The belt can be readily replaced by elevating the rollers 68, 70 atthe opposite side of the induction unit from servomotor 72, wherein thebelt can be readily removed and replaced with a new belt without thenecessity for disassembling a significant portion of frame 52.

Induction system 30 b, illustrated in FIGS. 3-5, is a single-lineinduction unit. A dual-line induction system 30 a, illustrated in FIGS.6-9, includes two induction units 32 which are substantially identicalin mechanical construction to each other and to the induction unit ininduction system 30 b. However, a master unit 78 includes a mastercontrol 64 a which includes the microcomputer for operating both masterunit 78 and slave unit 80. Slave unit 80 includes a slave control 64 bwhich includes control input devices 56 b for controlling the operationof slave unit 80. It also includes the input and output circuitry foroperating of the slave unit 80. However, as set forth above, themicrocomputer is positioned in control 64 a of master unit 78.Multiple-line induction system 30 a includes a status indicator 58 whichindicates the status of the induction units making up the inductionsystem.

Each induction unit 32 receives product from a product source 46, whichmay be a belt conveyor, or the like, which may not have the capabilityfor accumulation upstream of the induction system. The ability toeliminate upstream accumulation makes possible the use of an inductionsystem with belt conveyors, which are capable of handling product thatcannot be optimally handled by roller conveyors. However, it should beunderstood that the invention may be used with other types of productsource, including roller conveyors and units incorporating 98accumulation.

Each induction unit is logically divided into a series of conveyingunits designated 1-8 with the lower numbers towards the receiving end 34and the higher numbers towards the discharge 36. In the illustratedembodiment, eight conveying units are utilized. However, the modularnature of the invention allows the number of conveying units to begreater than or less than eight conveying units depending upon theapplication. In the case of a single-line induction system 30 b, theconveying units are designated A1-A8. In the case of a multiplyinginduction system 30 b, the conveying units are designated A1-A8 for aprimary line 83 and B1-B8 for a secondary line 85. As is conventional,the products discharged at discharge end 36 are mechanically merged at42.

Continuous member 26 includes an encoder 82 which may generate pulsescorresponding to movement of the continuous member. Each induction unit32 is synchronized with the continuous member 26 such that product maybe booked to positions on continuous member 26, which preferablycorresponds with individual pusher shoes or carriers 50. This isaccomplished by establishing synchronization at an upstream one of theconveying units and establishing synchronization as the product isadjusted to coincide substantially with the booked position ofcontinuous member 26. In the illustrative embodiment, synchronizationoccurs as early as the second conveying unit A2, B2 and preferably nolater than the third conveying unit A3, B3.

A photo-eye 76 is placed at the upstream end of each conveying unit 38.The photo-eye of the second conveying unit is used to detect the lengthof the product. An additional photo-eye is positioned at the dischargeend 46 in order to inform the merge section 42 about the movement of theproduct being discharged from the induction unit. Product source 46 hasa speed that is slower than the speed of continuous member 26 in orderto obtain a gap between the product during the transition from theproduct source to the upstream conveying unit A1, B1. The upstreamconveying unit A1, B1 has a constant speed in order to produce a gapbetween product. The second upstream conveying unit A2, B2 has a speedequal to conveying unit A1, B1 during the transfer phase between A1, B1to A2, B2 in order to provide a correct measurement of the productlength. Conveying units A3, B3 through A8, B8 all have belts withnominal speeds that are substantially equal to the speed of continuousmember 26. All of the conveying units are speed closed-loop-regulated toobtain correct loading and synchronization with the booked position ofthe continuous member. Because the speed of continuous member 26 maychange during the sortation process, as a result of jams, excessiveloading, and the like, the target speeds of the conveying units makingup the induction unit 32 may change in order to accommodate the changesin speed of the continuous member. In particular, at least one inductionunit in the induction system follows the speed of continuous member 26.The induction unit starts substantially as soon as the continuous memberis moving and decreases in speed only when the continuous memberdecreases in speed. In the case of a multiple induct system, the otherinduction unit may be capable of decreasing in speed irrespective of thespeed of the continuous member.

After a product has been accelerated on conveying unit A1, B1 to draw agap and the product is measured as to position and length as it movesonto conveying unit A2, B2, a position on continuous member 26, 26′ isbooked for that product. In the case of a linear sorter, as illustratedin FIG. 1, the product is booked with respect to a logical cell, whichpreferably is the leading edge of one of the pusher shoes on thecontinuous member 26. Because of the nature of the sorter, there is noproduct recirculating around the continuous member. Therefore, theposition on the continuous member, or logical cell, is booked to thenext available pusher shoe, taking into account any gap necessarybetween product on the sorter. In the case of a carousel-type sorter25′, the product is booked to a carrier 50 which should be available bythe time that carrier reaches the induct unit. As previously set forth,the control is capable of booking to a carrier which is presentlycarrying a product, if that product is to be discharged prior toreaching the induct system. If the product cannot be inducted to acarrier after that carrier is booked, such as where the carrier iscarrying a product at the induct due to the destination being full, orthe like, the booking is cancelled and a new booking is made for thatproduct.

Once a booking is made for a product on a conveying unit close to theproduct source, the remaining conveying units are used to adjust theposition of that product to that of the logical cell, or carrier, towhich the product is booked. This is possible because of the encoder 82and the speed closed-loop regulation of the conveying units which allowthe necessary adjustments to the product in order to be discharged tothe continuous unit 26, 26′ in a manner to be positioned at the logicalcell or carrier booked for that product.

Advantageously, the regulation scheme of conveying units 38 allow theinducting of product having a length that is greater than the length ofany of the belts 66 of the conveying units 38. This increases the rangeof product that may be handled by the induction system.

In order to induct product, induction system 30, 30 a, 30 b carries outan induction process 84 (FIG. 14). Induction process 84 begins at 86when the induction unit, or all induction units in the case of amultiple-line induction system, are in a regulation phase. The processincludes generating an uncontrolled gap between the product, andparcels, on the upstream-most conveying unit A1, B1. The control thenevaluates the length of the product, or parcel, (90) at the nextdownstream A2, B2 and books the logical cell or carrier for that productor parcel. The remaining conveying units A3, B3 through A8, B8 adjustthe parcel position to the appropriate logical cell or carrier bookedfor that product (92).

Regulation of the upstream-most belt A1, B1 is achieved according to acontrol procedure 94 (FIG. 15). Control procedure 94 begins by aninitialization 96 at which the belt 66 is operated at its nominal speedfor a period of time. The time period is defined as 1.5 times the lengthof the belt divided by the nominal speed (98). At the end of this time,the belt should be empty of product. The belt then continues to run atthe nominal speed until the initialization phase of all of the otherdownstream belts is complete and the sorter is synchronized (100).Initialization is then complete, and the status of the conveying unitA1, B1 is changed to the regulation phase 102. Upon entering regulationphase 102, the belt runs at nominal speed in order to generate anunregulated gap between articles or parcels (104).

For the next downstream conveying unit A2, B2, a control procedure 106(FIG. 16) begins with initialization at 108, at which time the belt isoperated at nominal speed for a time period that is defined as 1.5 timesthe belt length divided by its nominal speed (110). At the end of thisperiod, the belt should be empty. The belt continues to run at nominalspeed until the initialization phase of all of the other belts iscomplete and the sorter is synchronized (112). The status of theconveying unit is changed to the regulation phase at 114, and the beltruns at nominal speed until a photo-eye detects an incoming product andstarts measurement of the length and/or position of the product (116).Parcel, or product, measurement is carried out at 118 by the belt movingat its nominal speed with the position encoder being incremented untilthe photo-eye is obscured. When the photo-eye is no longer obscured, thecontrol is able to determine the length and/or position of the parceland a request for a logical cell or carrier is issued. The status of thebelt changes to that of a free belt (116).

A control routine 120 for the remaining conveying units A3, B3 throughA7, B7 is illustrated at 120 (FIG. 17). The control procedure begins atinitialization 122, wherein the corresponding belt starts at its nominalspeed for a period of time defined as 1.5 times the belt length dividedby nominal speed (124). At the end of this time period, the belt shouldbe empty and continues to run at nominal speed until the initializationphase of all of the other belts is complete and the sorter issynchronized (126). The status of the corresponding belt is changed tothe regulation phase at 128. The belt runs at nominal speed until aphoto-eye detects an incoming product, or parcel, checks its positionand calculates a first correction (130) to position the product at thebooked logical cell or carrier for that product on the continuousmember. The belt runs at nominal speed waiting for the start of thecorrection to begin at 132. The correction begins when the center of theparcel arrives on that conveying unit. The conveying unit then goesthrough a master regulation (134) and a slave regulation (136). Duringmaster regulation, the parcel is translated onto the conveying unit. Theconveying unit is deemed to have received the parcel when thecorresponding photo-eye is blocked. During the slave regulation phase,the conveying unit assists the previous upstream conveying unit. Thecenter of gravity of the parcel, or product, may still be on thedownstream belt, but the parcel is still considered to be in transit.During the master regulation, the speed of the conveying unit isadjusted according to the position required and the parcel length.During slave regulation, the belt moves at the same speed of theprevious upstream belt that is adjusting the parcel position. Masterregulation begins when the parcel is incoming without waiting for thecenter of the parcel to arrive. From the slave regulation, the systemgoes to master regulation when a new product leaves the conveying unit,the conveying unit returns to nominal speed.

Referring to FIG. 17, during master regulation, the belt runs at thespeed required to implement the correction calculated at 130. This iscarried out until the center of gravity of the parcel or product, is onthe conveying unit or until a request from the closest upstream-mostbelt is received. When a request from the closest upstream belt isreceived, the slave regulation routine 136 causes the belt to run at thespeed of the previous upstream belt until the parcel is completely offof the upstream conveying unit or until the center of gravity of theproduct is on the controlled conveying unit. While the controlled unitis in slave regulation, the correction is again estimated.

When the product reaches the last conveying unit A8, B8, a controlprocedure 138 is performed (FIG. 18). The procedure begins withinitialization at 140, at which time the belt of the last conveying unitA8, B8 is operated at nominal speed for a period of time defined as 1.5times the belt length divided by nominal speed (142). At the end of thistime period, the belt is considered empty. The belt continues to run atnominal speed (144) until the initialization phase of all of the otherbelts is complete and the sorter is synchronized. The status of thisbelt is changed to the regulation phase at 146. The belt runs at nominalspeed at 148 until a photo-eye detects that an incoming product isreceived. The conveying unit A8, B8 checks the position of the productand estimates a correction to discharge the product to the bookedlogical cell or carrier. During a start correction phase 150, the beltruns at nominal speed waiting for the start of the correction. Duringmaster regulation (152), the belt runs at the calculated correctionspeed until the photo-eye of the discharge end 36 is unblocked. When thephoto-eye is blocked, a load parcel on merging routine 154 is performed.When the photo-eye is blocked, the belt runs at a speed that iscontrolled to manage alignment of the parcel with the booked pusher,logical cell, or, in the case of a carousel sorter, the booked carrier.After that, if a new parcel is detected, the control returns to a freebelt (148) status. Otherwise, the belt returns to the master regulation(152) status.

If one or both induction units, or lines, are stopped, an activationsequence 160 is carried out (FIG. 19). When the activation sequence isinitiated at 162, it is determined at 164 whether both lines arestopped. If both lines are not stopped, the product source 46 of theactive induction unit is stopped at 166. The active induction unitcontinues to induct product to the continuous member until the inductionunit is empty (168). The line that is stopped is started at 170 with theindividual conveying units 38 being started according to a schedule. Itis then determined at 172 whether the upstream-most conveying unit A1,B1 is running at nominal speed. When conveying unit A1, B1 is running atnominal speed, the remaining conveying units are started and processedto the regulation phase at 174.

If it is determined at 164 that both lines are stopped, primary line 83is started at 176 utilizing a schedule for starting the units. When itis determined at 178 that the upstream-most conveying unit A1 is runningat nominal speed, the remaining conveying units are started at 180 andprocessed to the regulation phase. Then secondary line 85 is startedutilizing the same sequence at 182. It is then determined at 184 whetherthe upstream-most conveying unit B1 is running at nominal speed. When itis, the remaining conveying units for the secondary line are started andprocessed to the regulation phase at 186.

Induction system 30, 30 a, 30 b includes a mode defined as “stop notallowed.” When primary line 83 of multiple-line induct 30 a isconfigured as “stop not allowed,” the corresponding induction unitstarts as soon as the continuous member is moving. When in such “stopnot allowed” mode, the primary line stops only when the continuousmember is stopped. As such, the primary line in the “stop not allowed”mode follows the motion of the continuous member, receiving product fromthe product source and moving the product on the continuous member witha sufficient gap with a downstream product. In the case where productcannot be placed on the continuous member with the correct gap, theadjustment to the belt speeds will be suspended and one or more itemswill be loaded to the continuous member without the correct gap.Preferably, the items loaded to the continuous member without thecorrect gap will be sent to recirculation line 44.

A control routine 200 for the primary line 83 begins at 202 bydetermining at 204 whether a correct gap can be established for itemsbeing loaded to the induction of the primary line (FIG. 20). If it isdetermined at 204 that correct gaps can be established, the controlreturns to 202 where an ongoing inquiry is made whether correct gaps canbe established. When it is determined at 204 that a correct gap cannotbe established for product being loaded to the induction unit, adetermination is made at 206 whether the primary line is in the “stopnot allowed” mode. If it is determined at 206 that the primary line isin the “stop not allowed” mode, the secondary line is stopped at 208 anda determination is made at 210 whether, with the secondary line stopped,it is possible to achieve a correct gap for product discharged to thecontinuous member. If it is determined at 210 that a correct gap can beachieved, the control returns to activation sequence 160 in order torestart the secondary line.

If it is determined at 210 that a correct gap cannot be achieved withthe secondary line stopped, control proceeds to 212 where the conveyingunits are operated at nominal speed without an attempt to adjust thebelts for achieving proper gap. The control then sends one or moreproducts to the recirculation line at 214 and restarts belt adjustmentsat 216.

The control then determines at 218 whether more than a particularpercentage of the product is in recirculation. Because productdischarged in a continuous member without adequate gap is sent torecirculation and the recirculation returns the product to the inductionunit, it is possible for the number of products that cannot beadequately gapped to increase in the sortation system. When it isdetermined at 218 that more than a particular percentage of the productis in recirculation, the mode of the primary line is changed at 220. Inparticular, the “stop not allowed” mode is changed to “stop allowed” andthe “gap not controlled” mode is changed to “gap-controlled.” If it isdetermined at 218 that the percentage of product in recirculation isless than the given percentage, control returns to 202. In theillustrated embodiment, the given percentage in recirculation is 30percent, but greater or lesser percentages may be utilized.

When it is determined at 206 that the primary line is in the “stopallowed” mode, it is determined at 222 whether the primary line is in a“gap controlled” mode. If the primary line is in a “stop allowed” mode,but not in a “gap controlled” mode, control proceeds to 212 where beltadjustments are suspended and items that cannot be properly gapped aresent to recirculation. If it is determined at 222 that the primary lineis in the “gap controlled” mode, the primary line is stopped at 224 foritems that cannot be properly gapped. Activation sequence 160 isperformed in order to return the primary line to regulation status.

A control routine 230 for controlling the secondary line 85 begins at232 by determining at 234 whether a correct gap can be achieved foritems loaded to the induction unit making up the secondary line. If so,control returns to 232 where the system continues to repeatedly checkfor correct gaps. When it is determined at 234 that a correct gap cannotbe achieved for the items being loaded to the induction unit, it isdetermined at 236 whether the primary line is in the “stop allowed”mode. If it is determined that the primary line is in the “stop notallowed” mode, the secondary line is stopped at 238 and activationsequence is performed at 160 in order to bring the secondary line toregulation status.

If it is determined at 236 that the primary line is in the “stopallowed” mode, it is determined at 240 whether the system is in a “gapcontrolled” mode. If it is determined at 240 that the system is in a“gap controlled” mode, the secondary line is stopped at 242 in order toavoid discharging an improperly gapped product to the continuous member.Activation sequence is then performed at 160 in order to bring thesecondary line to regulation status.

If it is determined at 240 that the system is not in the “gapcontrolled” mode, belt adjustments are suspended at 244 and anyimproperly gapped items are sent to the recirculation line at 246. Beltadjustment is restarted at 248, and it is determined at 250 whether morethan a given percentage of product is in recirculation. If it isdetermined at 250 that more than the given percentage of product is inrecirculation, the induction system is changed to the “gap controlled”mode at 252. If it is determined at 250 that less than the givenpercentage of product is in recirculation, the control returns to 232.

The result is that if the primary line is configured as “stop allowed”and in the “gap controlled” mode, the line must always place the producton the continuous member system with the correct gap. If the gap cannotbe reached, the primary line and the relevant upstream-conveyor willstop. If the primary line is in the “stop not allowed” mode and in the“no gap” mode, it is necessary to avoid stopping the primary line, ifpossible. In case items cannot be placed on the continuous member withthe correct cap, the belt adjustments will be suspended and one or moreitems will be loaded without the correct cap and sent to therecirculating line. The system will automatically change the mode ofworking from “no gap” to “gap controlled” if more than the pre-selectedpercentage of items is sent to the recirculating line.

The secondary line also includes two modes of working when the primaryline is in the “stop allowed” mode. In the “gap controlled” mode, thesecondary line must always place the items on the continuous member withthe correct gap. If the gap cannot be reached, the secondary line andthe relevant upstream conveyor will stop. In the “no gap” mode, it isnecessary to avoid stopping the secondary line, if possible. In caseitems cannot be placed on the continuous member with the correct gap,the belt adjustments will be suspended and one or more items will beloaded without the correct gap and sent to the recirculating line. Thesystem will automatically change the mode of working from “no gap” to“gap controlled” if more than the selected percentage of items is sentto the recirculating line. In any case, the secondary line must stop ifthe primary line is configured as “stop not allowed” and for some reasonit is not possible to load items on the continuous member with a minimumconfigurable gap.

The present invention thus is capable of providing a priority lane forwhich the product is handled in a fashion which gives priority toproduct supplied to that lane over product supplied to other lane orlanes. This is desirable, for example, if a deadline in handling productfor one lane is approaching or if product on one lane must be handled ina short period of time. The present patent discloses an induction systemwhich is capable of tracking the speed of the sorter and providessynchronization with the sorter during restarting of the sorter afterthe sorter has been shutdown. This, advantageously, obviates thenecessity for accumulation upstream of the induction system as well asin a re-circulation line for re-circulating product that s notadequately gapped.

The conveying surface of the conveying units making up the inductionunits operate in a manner which reduces the slowing of product on theinduct, over those of the prior art, and pushes any such slowing furtherupstream on the induction unit. Advantageous, product can be inductedhaving lengths that exceed the lengths of the conveying units of theinduct.

The present invention also provides an induct unit mechanized structurewhich is both compact and easy to maintain. Furthermore, a multiple lineinduct can be controlled in a master/slave fashion with a singlecomputer controlling operation of multiple lines.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the inventionwhich is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A sortation system,comprising: a sorter including a continuous member defining a pluralityof transport positions of said continuous member; a plurality of sortdestinations for receiving product discharged from said continuousmember; and an induction system comprising at least one induction unithaving a receiving end for receiving product from a product source and adischarge end for discharging product to said continuous member, said atleast one induction unit including a plurality of tandem conveying unitsbetween said receiving end and said discharge end and a controlcontrolling said conveying units, wherein said control books at leastone transport position for receipt of product from said at least oneinduction unit, wherein said control books a transport position for aproduct when that product is at a booking conveying unit and adjustsrelative spacing between a product and the respective transport positionbooked for that product on a plurality of adjusting conveying unitsdownstream of said booking conveying unit, said control operating eachof said adjusting conveying units in a master regulation mode and aslave regulation mode, during said master regulation mode a speed of arespective one of said adjusting conveying units being adjusted tocorrect relative spacing between a product and the respective transportposition booked for that product, during said slave regulation mode thespeed of the respective one of said adjusting conveying units beingregulated according to the speed of the one of said adjusting conveyingunits upstream of the respective one of said adjusting conveying units.2. The sortation system in claim 1 wherein said sorter comprises acarousel sorter and said continuous member comprises a plurality ofcarriers joined together in a substantially continuous chain, saidcarriers defining said transport positions.
 3. The sortation system inclaim 2 wherein said carousel sorter comprises a cross-belt sorter. 4.The sortation system in claim 2 wherein said carousel sorter comprises atilt-tray sorter.
 5. The sortation system in claim 1 wherein said sortercomprises a linear sorter and said continuous member comprises aconveying surface and a plurality of diverts along said conveyingsurface, and diverters defining said transport positions.
 6. Thesortation system in claim 5 wherein said sorter comprises a positivedisplacement sorter.
 7. The sortation system in claim 1 includingproduct sensors at said conveying units.
 8. The sortation system inclaim 1 including a product source feeding product to an upstream one ofsaid conveying units and wherein said adjusting conveying unitssubstantially operates at a speed that is greater than or equal to aspeed of said product source.
 9. The sortation system in claim 8 whereinsaid product source comprises belt conveyors.
 10. The sortation systemin claim 8 wherein said product source substantially excludes productaccumulation.
 11. The sortation system in claim 1 wherein speeds of saidconveying units are synchronized with said continuous member so thatsaid conveying units feed product to said continuous member with a speedof said continuous member.
 12. The sortation system in claim 1 whereinsaid continuous member operates at a variable speed and wherein speedsof said conveying units vary at least in part with the speed of saidcontinuous member.
 13. The sortation system in claim 1 wherein saidcontrol maintains any booking of transport positions for product on saidat least one induction unit notwithstanding variation in speed of saidcontinuous member.
 14. The sortation system in claim 1 wherein saidcontrol maintains any booking of transport positions for product on saidat least one induction unit notwithstanding a substantial halt in speedof said continuous member.
 15. The sortation system in claim 1 whereinsaid conveying units are closed-loop regulated.
 16. The sortation systemin claim 1 wherein said conveying units are belt conveyors.
 17. Thesortation system in claim 1 wherein said conveying units have particularlengths and wherein said at least one induction unit is adapted todischarging product to said continuous member having a dimension that isgreater than said particular lengths.
 18. The sortation system in claim1 wherein said induction system comprises at least two induction units,wherein said induction units discharge product to said continuousmember.
 19. The sortation system in claim 18 wherein at least one ofsaid induction units has a nominal speed that follows a speed of saidcontinuous member including starting as soon as said continuous memberis moving and decreasing in nominal speed only when said speed of saidcontinuous member decreases.
 20. The sortation system in claim 19wherein said at least one of said induction units discharges product tosaid continuous member with insufficient gap between product if asufficient gap cannot be achieved.
 21. The sortation system in claim 20wherein said sorter discharges product with an insufficient gap to arecirculation line.
 22. The sortation system in claim 19 wherein theother of said induction units does not follow said continuous member andcan decrease in speed irrespective of said continuous member.
 23. Thesortation system in claim 19 wherein said product source substantiallyexcludes product accumulation.
 24. The sortation system in claim 19wherein said product source comprises belt conveyors.
 25. A method ofinducting product to a sorter, the sorter including a continuous memberdefining a plurality of transport positions of said continuous memberand a plurality of sort destinations for receiving product dischargedfrom said continuous member, comprising: providing a plurality of tandemconveying units; receiving product with said conveying units from aproduct source and discharging product from said conveying units to thecontinuous member; booking at least one transport position for receiptof a product from said conveying units, including booking the productwhen that product is at a booking conveying unit; and adjusting relativespacing between a product and the respective transport position bookedfor that product when the product is on a plurality of adjustingconveying units downstream of said booking conveying unit, saidadjusting relative spacing including operating each of said adjustingconveying units in a master regulation mode and a slave regulation mode,during said master regulation mode a speed of a respective one of saidadjusting conveying units being adjusted to correct relative spacingbetween a product and the respective transport position booked for thatproduct, during said slave regulation mode the speed of the respectiveone of said adjusting conveying units being regulated according to thespeed of the one of said adjusting conveying units upstream of therespective one of said adjusting conveying units.
 26. The method ofinducting of claim 25 wherein said continuous member comprises aplurality of carriers joined together in a substantially continuouschain, said carriers defining said transport positions.
 27. The methodof inducting of claim 26 wherein said carousel sorter comprises across-belt sorter.
 28. The method of inducting of claim 26 wherein saidcarousel sorter comprises a tilt-tray sorter.
 29. The method ofinducting of claim 25 wherein said continuous member comprises aconveying surface and a plurality of diverters along said conveyingsurface, said diverters defining said transport positions.
 30. Themethod of inducting of claim 29 wherein said diverters and saidconveying surface define a positive displacement sorter.
 31. The methodof inducting of claim 30 wherein said product source substantiallyexcludes product accumulation.
 32. The method of inducting of claim 25including sensing product at said conveying units.
 33. The method ofinducting of claim 25 including feeding product from a product source toan upstream one of said conveying units and operating said adjustingconveying units substantially at a speed that is greater than or equalto a speed of said product source.
 34. The method of inducting of claim33 wherein said product source comprises belt conveyers.
 35. The methodof inducting of claim 25 including synchronizing speeds of saidconveying units with said continuous member so that said conveying unitsfeed product to said continuous member with a speed of said continuousmember.
 36. The method of inducting of claim 25 including operating saidcontinuous member at a variable speed and varying speeds of saidconveying units at least in part with the speed of said continuousmember.
 37. The method of inducting of claim 25 including maintainingany booking of transport positions for product on said at least oneinduction unit notwithstanding variation in speed of said continuousmember.
 38. The method of inducting of claim 25 including maintainingany booking of transport positions for product on said at least oneinduction unit notwithstanding a substantial halt in speed of saidcontinuous member.
 39. The method of inducting of claim 25 includingclosed-loop regulating speeds of said conveying units.
 40. The method ofinducting of claim 25 wherein said conveying units are belt conveyors.41. The method of inducting of claim 25 wherein said conveying unitshave particular lengths and including at least occasionally dischargingproduct from said at least one induction unit to said continuous memberhaving a dimension that is greater than said particular lengths.
 42. Themethod of inducting of claim 25 including providing another plurality oftandem conveying units, and including discharging product from saidplurality of tandem conveying units and said another plurality of tandemconveying units to said continuous member.
 43. The method of inductingof claim 42 including following a speed of said continuous member with anominal speed of at least one of said plurality of tandem conveyingunits and said another plurality of tandem conveying units includingstarting said at least one of said plurality of tandem conveying unitsand said another plurality of tandem conveying units as soon as saidcontinuous member is moving and decreasing in nominal speed said atleast one of said plurality of tandem conveying units and said anotherplurality of tandem conveying units only when said speed of saidcontinuous member decreases.
 44. The method of inducting of claim 43including discharging product from said at least one of said pluralityof tandem conveying units and said another plurality of tandem conveyingunits to said continuous member with insufficient gap between product ifa sufficient gap cannot be achieved.
 45. The method of inducting ofclaim 44 including recirculating product discharged with an insufficientgap.
 46. The method of inducting of claim 43 including at leastoccasionally decreasing a speed of the other of said plurality of tandemconveying units and said another plurality of tandem conveying unitsirrespective of the speed of said continuous member.